The dual supply voltages operationable circuit is the trend of the integrated circuit (IC) design, and more and more circuit are designed for normally operating with dual supply voltages even multiple supply voltages. Therefore, the application of supply voltage conversion circuit is quite popular, such as communication, wireless local area network (WLAN), analog-to-digital circuit in optical fiber communications, digital video disc (DVD), liquid crystal display (LCD) driving circuit, motherboard, central processing unit (CPU), generally consumer electronic apparatus, or consumer integrated circuit all need this kind of conversion circuit. Hence, if such conversion circuit is successfully designed and produced, it will bring unlimited trade.
In many IC design, the designed circuit must be operated under different supply voltages at the same time, and the external conversion circuit must be modified without changing the internal supply voltage and design of the circuit. Designing a dual supply voltages converter is expected for connecting the available supply voltage from external to core circuit, and, for example, typically 5V and 3.3V are successfully converted to 3.3V for internal circuit. Accordingly, the designed circuit will be competitive and tradable.
However, in the current IC design, a bandgap reference circuit or the traditional converter circuit is used in the most design of the dual supply voltages converter. In using bandgap reference circuit, the difference of the provided supply voltages cannot be too large such as a few hundreds of milivolts, and in using traditional converter circuit, the volume of whole circuit will be quite huge and cannot be integrated.